1 // SPDX-License-Identifier: GPL-2.0-or-later 2 /* Instantiate a public key crypto key from an X.509 Certificate 3 * 4 * Copyright (C) 2012 Red Hat, Inc. All Rights Reserved. 5 * Written by David Howells (dhowells@redhat.com) 6 */ 7 8 #define pr_fmt(fmt) "X.509: "fmt 9 #include <linux/module.h> 10 #include <linux/kernel.h> 11 #include <linux/slab.h> 12 #include <keys/asymmetric-subtype.h> 13 #include <keys/asymmetric-parser.h> 14 #include <keys/system_keyring.h> 15 #include <crypto/hash.h> 16 #include "asymmetric_keys.h" 17 #include "x509_parser.h" 18 19 /* 20 * Set up the signature parameters in an X.509 certificate. This involves 21 * digesting the signed data and extracting the signature. 22 */ 23 int x509_get_sig_params(struct x509_certificate *cert) 24 { 25 struct public_key_signature *sig = cert->sig; 26 struct crypto_shash *tfm; 27 struct shash_desc *desc; 28 size_t desc_size; 29 int ret; 30 31 pr_devel("==>%s()\n", __func__); 32 33 if (!cert->pub->pkey_algo) 34 cert->unsupported_key = true; 35 36 if (!sig->pkey_algo) 37 cert->unsupported_sig = true; 38 39 /* We check the hash if we can - even if we can't then verify it */ 40 if (!sig->hash_algo) { 41 cert->unsupported_sig = true; 42 return 0; 43 } 44 45 sig->s = kmemdup(cert->raw_sig, cert->raw_sig_size, GFP_KERNEL); 46 if (!sig->s) 47 return -ENOMEM; 48 49 sig->s_size = cert->raw_sig_size; 50 51 /* Allocate the hashing algorithm we're going to need and find out how 52 * big the hash operational data will be. 53 */ 54 tfm = crypto_alloc_shash(sig->hash_algo, 0, 0); 55 if (IS_ERR(tfm)) { 56 if (PTR_ERR(tfm) == -ENOENT) { 57 cert->unsupported_sig = true; 58 return 0; 59 } 60 return PTR_ERR(tfm); 61 } 62 63 desc_size = crypto_shash_descsize(tfm) + sizeof(*desc); 64 sig->digest_size = crypto_shash_digestsize(tfm); 65 66 ret = -ENOMEM; 67 sig->digest = kmalloc(sig->digest_size, GFP_KERNEL); 68 if (!sig->digest) 69 goto error; 70 71 desc = kzalloc(desc_size, GFP_KERNEL); 72 if (!desc) 73 goto error; 74 75 desc->tfm = tfm; 76 77 ret = crypto_shash_digest(desc, cert->tbs, cert->tbs_size, sig->digest); 78 if (ret < 0) 79 goto error_2; 80 81 ret = is_hash_blacklisted(sig->digest, sig->digest_size, "tbs"); 82 if (ret == -EKEYREJECTED) { 83 pr_err("Cert %*phN is blacklisted\n", 84 sig->digest_size, sig->digest); 85 cert->blacklisted = true; 86 ret = 0; 87 } 88 89 error_2: 90 kfree(desc); 91 error: 92 crypto_free_shash(tfm); 93 pr_devel("<==%s() = %d\n", __func__, ret); 94 return ret; 95 } 96 97 /* 98 * Check for self-signedness in an X.509 cert and if found, check the signature 99 * immediately if we can. 100 */ 101 int x509_check_for_self_signed(struct x509_certificate *cert) 102 { 103 int ret = 0; 104 105 pr_devel("==>%s()\n", __func__); 106 107 if (cert->raw_subject_size != cert->raw_issuer_size || 108 memcmp(cert->raw_subject, cert->raw_issuer, 109 cert->raw_issuer_size) != 0) 110 goto not_self_signed; 111 112 if (cert->sig->auth_ids[0] || cert->sig->auth_ids[1]) { 113 /* If the AKID is present it may have one or two parts. If 114 * both are supplied, both must match. 115 */ 116 bool a = asymmetric_key_id_same(cert->skid, cert->sig->auth_ids[1]); 117 bool b = asymmetric_key_id_same(cert->id, cert->sig->auth_ids[0]); 118 119 if (!a && !b) 120 goto not_self_signed; 121 122 ret = -EKEYREJECTED; 123 if (((a && !b) || (b && !a)) && 124 cert->sig->auth_ids[0] && cert->sig->auth_ids[1]) 125 goto out; 126 } 127 128 ret = -EKEYREJECTED; 129 if (strcmp(cert->pub->pkey_algo, cert->sig->pkey_algo) != 0) 130 goto out; 131 132 ret = public_key_verify_signature(cert->pub, cert->sig); 133 if (ret < 0) { 134 if (ret == -ENOPKG) { 135 cert->unsupported_sig = true; 136 ret = 0; 137 } 138 goto out; 139 } 140 141 pr_devel("Cert Self-signature verified"); 142 cert->self_signed = true; 143 144 out: 145 pr_devel("<==%s() = %d\n", __func__, ret); 146 return ret; 147 148 not_self_signed: 149 pr_devel("<==%s() = 0 [not]\n", __func__); 150 return 0; 151 } 152 153 /* 154 * Attempt to parse a data blob for a key as an X509 certificate. 155 */ 156 static int x509_key_preparse(struct key_preparsed_payload *prep) 157 { 158 struct asymmetric_key_ids *kids; 159 struct x509_certificate *cert; 160 const char *q; 161 size_t srlen, sulen; 162 char *desc = NULL, *p; 163 int ret; 164 165 cert = x509_cert_parse(prep->data, prep->datalen); 166 if (IS_ERR(cert)) 167 return PTR_ERR(cert); 168 169 pr_devel("Cert Issuer: %s\n", cert->issuer); 170 pr_devel("Cert Subject: %s\n", cert->subject); 171 172 if (cert->unsupported_key) { 173 ret = -ENOPKG; 174 goto error_free_cert; 175 } 176 177 pr_devel("Cert Key Algo: %s\n", cert->pub->pkey_algo); 178 pr_devel("Cert Valid period: %lld-%lld\n", cert->valid_from, cert->valid_to); 179 180 cert->pub->id_type = "X509"; 181 182 if (cert->unsupported_sig) { 183 public_key_signature_free(cert->sig); 184 cert->sig = NULL; 185 } else { 186 pr_devel("Cert Signature: %s + %s\n", 187 cert->sig->pkey_algo, cert->sig->hash_algo); 188 } 189 190 /* Don't permit addition of blacklisted keys */ 191 ret = -EKEYREJECTED; 192 if (cert->blacklisted) 193 goto error_free_cert; 194 195 /* Propose a description */ 196 sulen = strlen(cert->subject); 197 if (cert->raw_skid) { 198 srlen = cert->raw_skid_size; 199 q = cert->raw_skid; 200 } else { 201 srlen = cert->raw_serial_size; 202 q = cert->raw_serial; 203 } 204 205 ret = -ENOMEM; 206 desc = kmalloc(sulen + 2 + srlen * 2 + 1, GFP_KERNEL); 207 if (!desc) 208 goto error_free_cert; 209 p = memcpy(desc, cert->subject, sulen); 210 p += sulen; 211 *p++ = ':'; 212 *p++ = ' '; 213 p = bin2hex(p, q, srlen); 214 *p = 0; 215 216 kids = kmalloc(sizeof(struct asymmetric_key_ids), GFP_KERNEL); 217 if (!kids) 218 goto error_free_desc; 219 kids->id[0] = cert->id; 220 kids->id[1] = cert->skid; 221 222 /* We're pinning the module by being linked against it */ 223 __module_get(public_key_subtype.owner); 224 prep->payload.data[asym_subtype] = &public_key_subtype; 225 prep->payload.data[asym_key_ids] = kids; 226 prep->payload.data[asym_crypto] = cert->pub; 227 prep->payload.data[asym_auth] = cert->sig; 228 prep->description = desc; 229 prep->quotalen = 100; 230 231 /* We've finished with the certificate */ 232 cert->pub = NULL; 233 cert->id = NULL; 234 cert->skid = NULL; 235 cert->sig = NULL; 236 desc = NULL; 237 ret = 0; 238 239 error_free_desc: 240 kfree(desc); 241 error_free_cert: 242 x509_free_certificate(cert); 243 return ret; 244 } 245 246 static struct asymmetric_key_parser x509_key_parser = { 247 .owner = THIS_MODULE, 248 .name = "x509", 249 .parse = x509_key_preparse, 250 }; 251 252 /* 253 * Module stuff 254 */ 255 static int __init x509_key_init(void) 256 { 257 return register_asymmetric_key_parser(&x509_key_parser); 258 } 259 260 static void __exit x509_key_exit(void) 261 { 262 unregister_asymmetric_key_parser(&x509_key_parser); 263 } 264 265 module_init(x509_key_init); 266 module_exit(x509_key_exit); 267 268 MODULE_DESCRIPTION("X.509 certificate parser"); 269 MODULE_AUTHOR("Red Hat, Inc."); 270 MODULE_LICENSE("GPL"); 271